Ryan Stevens was only 36, but a diagnosis of Crohn's disease left him with overwhelming lethargy and chronic diarrhea every time he ate a morsel of food. The former college swimmer lost 65 pounds and spent most of his days on the couch.

"I was 120 pounds and I am usually 185," said Stevens, who once trained for triathlons. "If I had walked on the set of 'Walking Dead,' they would have cast me right away. They wouldn't even have to use make-up."

But in 2011, doctors at the Cleveland Clinic performed three surgeries, removing five feet of his colon -- a drastic step when medications fail to stop the progression of the disease.

Today, at 40, Stevens is feeling strong, and on July 27, he plans to swim 24 miles across Lake Erie to raise awareness about Crohn's disease, a devastating autoimmune condition that can cause persistent diarrhea, pain and, at times bleeding. It can also affect the joints, eyes, skin, and liver.

Stevens' swim will take him from Long Port, Ontario, in Canada to Free Port Beach in Pennsylvania. His goal is to raise $10,000, which will go to Crohn's and colitis research at Cleveland Clinic. So far he has raised $2,500.

"It's an invisible and relentless disease," said Stevens, who lives with his wife Samantha, and 12-year-old son Riley in Maumee. "Just because you look fine, you really aren't."

Crohn's Disease is a form of inflammatory bowel disease (IBD) in which the intestine becomes inflamed and develops sores. It causes disruption in the normal function of the bowel and blockages that inhibit the ability to absorb nutrients. Patients can also develop ulcers in the walls of the intestine.

IBD is one of the five most prevalent gastrointestinal diseases in the United States, affecting as many as 1.4 million Americans, according to the Centers for Disease Control and Prevention. Over the long term, up to 75 percent of patients with Crohn's disease will require surgery.

Some people with Crohn's can be managed with medications, but in the long term, 75 percent of cases, like Ryan's, involve surgery to remove all or some of the colon. Many people are too embarrassed to even talk about the disease.

"Crohn's is a terrible disease," said Dr. Meagan Costedio, a colorectal surgeon at Cleveland Clinic who treated Stevens. "In the way the body is supposed to work, when it senses something -- a virus or bacteria, it makes antibodies called antigens that fight it off. But in this disease, the body senses the small bowel as an antigen and attacks it. We don't know why this happens."

Most of the time there are no genetic markers for Crohn's disease. No one in Stevens' family has the disease. His has been a particularly virulent form.

"Some people take just mild meds and they work perfect," Costedio said. "Some people flare and it doesn't matter what we do, it gets better on its own. And some don't get better, as is the case with Ryan. His Crohn's mainly affects his colon and he would get sick every time he ate."

Many patients have diarrhea up to 20 times a day and often bleed so much they require blood transfusions, she said. "In addition, you feel like crap. People are very sick and very miserable."

"I thought maybe it was the stomach flu but in a couple of days it hadn't cleared up," he said. "My wife, who I credit with keeping me alive through all this, said, 'Go see a doctor, you dummy.'"

At first, his general practitioner agreed it was the flu and told him to eat yogurt and he'd be better in a week. But Stevens didn't get better, and was referred to a gastroenterologist who discovered a fissure and fistula in the anus.

By 2009, he was losing about 10 pounds a week. Eventually, a colonoscopy and a follow-up biopsy showed Crohn's disease.